[GHC] #12370: Implement LetUp in DmdAnal (or document why we do not do it)

[GHC]

#12370: Implement LetUp in DmdAnal (or document why we do not do it)
-------------------------------------+-------------------------------------
        Reporter:  nomeata           |                Owner:
            Type:  task              |               Status:  patch
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D2395
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by Joachim Breitner <mail@…>):

 In [changeset:"45d8f4eb2bf2fcb103517d064e7ba1e491a66f4c/ghc"
 45d8f4eb/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="45d8f4eb2bf2fcb103517d064e7ba1e491a66f4c"
 Demand analyser: Implement LetUp rule (#12370)

 This makes the implementation match the description in the paper more
 closely: There, a let binding that is not a function has first its body
 analised, and then the binding’s RHS. This way, the demand on the bound
 variable by the body can be fed into the RHS, yielding more precise
 results.

 Performance measurements do unfortunately not show significant
 improvements or regessions.

 Differential Revision: https://phabricator.haskell.org/D2395
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12370#comment:7>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler